This is a brief discussion of the central concepts of small unit fighting in the medievalist setting.    This article is not a definitive guide and should not be read as such.  Rather, it is an attempt to stimulate thought and discussion on this subject.  In other words, if you've got something to say about this, then get together with some other folks and write an article about it.  This article represents the opinions of Jester of Anglesey and no one else.  That being said, read on…

Work as a team,
 Everything else we discuss will be subordinate to this principle. We are a mercenary group which fights in melees.  While individual fighting skill is to be encouraged and admired, we fight as a group, not a collection of individuals.  By cooperating effectively we can overcome opponents who, on an individual basis, are more skilled than us.
 There are many facets to teamwork.  Foremost among these is trust.  Each individual must trust everyone else to do their part in an intelligent manner.  This allows each person to focus on a single task, confident that they can devote their entire attention to that task and not have to worry about their back.  Trust is something that is earned over long periods of association and carries over into aspects other than combat.  For example: if you can't be trusted in camp, how can you be trusted on the battlefield?
 The association that produces trust also allows you to understand people, to know them.  Only by talking to people, by being around them can you begin to understand how they think, why they act the way they do.  In battle, this familiarity will translate into an increased ability to cooperate.  If you know that Bob McBob is an aggressive SOB who believes the best defense is a good offense, and you have fought with him before, then you can have a pretty good idea of how he will react in battle.  Know the people you fight with, your enemies as well as your friends.
 Never fight as an individual so long as one friend remains alive.  Work together to get the kills and accomplish the group's mission.  No action on the battlefield should be wasted.  Use your attack, for example, to create an opening for someone else.  You may not kill your opponent, but by moving his shield out of position you make it possible for the spearman two people down to gut him like a fish.  In the same vein, watch for the opportunities that your comrades create for you.  By working together two mediocre fighters can get as many or more kills than a good fighter who fights as an individual.  Every action you take should be intended in some way to help the group.

Communicate,
 Talk to the people around you.  Let the spearman know that you are coming up on their left to support them.  They might appreciate a hint about the four bad guys charging from behind them.  Identify targets for them.  Let them know when you're dead by dying loudly.  If you need help to take out a bad guy, let the folks around you know.  Pass on verbal commands from your commanders.  Do not yell out orders unless you are echoing a command or you are in charge, you'll just muddy the waters and confuse people (like me).

Fight the way you planned,
 Initiative is the ability to dictate the terms of a battle.  By making the enemy fight on your terms, you automatically gain an advantage.  You know what you are going to do and he has to try to figure that out and react.  He has to do two things, you only have to do one.  In the military they have a saying:  "Seize, retain, and exploit the initiative."  Never let the enemy push you around.  We are the wolves, they are the sheep.

Don't let the enemy use his resources,
 Tie up, destroy, or render ineffective the enemy's best assets.  Examples of this include:  pinning a unit that relies on mobility, ganging up on a particularly effective warrior, scattering or killing the archers, separating a leader from his unit, or going around the flank of a unit that relies on a tight shield wall.  This will force the enemy to deviate from their battle plan and allows you to seize the initiative.  Battle plans are often built around resources, when those resources are in some way removed the enemy plan falls apart and they are forced to improvise.  A good unit, one that practices together on a regular basis, can recover from this, but hodgepodge units formed of groups who don't know each other will be plunged into uncertainty and confusion.  Because our plans are based on organization and tactics we are less susceptible to such actions, and because we practice together on a regular basis we can recover more quickly.

Aggression,
 In his book "A Brief History of War", author John Keegan explores the time when warfare stopped being a ritual and became a business.  It happened when farmers, to whom hunting was a ritual to supplement food and who practiced herding on a small scale, encountered nomads, to whom hunting was a matter of survival and who practiced large scale herdin.  Since hunting was the model for warfare, the nomads quickly dominated their opponents in a tactical sense.  We can carry this principle forward in time and apply it to our situation.  We must place ourselves in the role of the hunter and dictate the terms of the engagement.  We place our opponents in the role of the prey and force them to react.  We herd them into groups, separate individuals from the group, and cut them down.  We drive the herd to a location of our choosing and slaughter them.  We do this by acting aggressively, by initiating action and executing it ruthlessly and decisively.
All actions on the battlefield should be carried out as violently and as ruthlessly as safely possible.  A melee is not a tournament.  We do not greet an enemy, ask him if he's comfortable, and then commence fighting.  We sweep down on our foes like a storm.  We overwhelm them, knock them down, and never give them a chance to rest or recover.  If we can't go through them, then we slash them as we move by or around.  When we are gone the wounded survivors should be trying, unsuccessfully, to figure out what just happened to them while we are halfway across the field cutting another unit to pieces.

Avoid a fair fight,
 A fair fight, for this purpose, is defined as a conflict between two opposing groups of approximately equal skill and status.  A fair fight is like a coin toss, you've got a fifty percent chance of winning or losing.  We want to win, so we do every thing that we are allowed to do according to the SCA rules of warfare to gain any advantage we can.  It isn't pretty, it isn't chivalrous, but it is effective.  We are here to fight according to the rules, and we are also here to win.  So we pick off two opponents with four of our fighters, or we bring in spears to pick a wounded shield-wall to pieces, or we mob Sir So-and-So with three guys while the rest of us wipe out his squires.  Some people will argue that this is  contrary to the spirit in which we fight in the SCA.  I disagree.  No one criticizes Sir Whitebelt when he maneuvers his opponent into opening up his guard.  We are simply applying the same concept to group combat.  We don't have to cheat or be unsafe to gain an advantage, we just have to be smart, quick, and practiced.

Maintain unit cohesion,
 It is impossible to define a standard of unit cohesion because it varies according to the circumstances.  The order for a woods battle will be very different from that of a bridge battle.  In general, you should be close enough that you can support the person to either side of you, so that your group of two, three, or four people can support the other group of people on either side of you.  You should be close enough that the enemy can't break your line and split the group.  But you should also be far enough apart to avoid losing room to maneuver.  Only through constant practice as a group can we personally learn this.  The only constant to this concept is, fight as a member of a team, not as an individual.

Be aware of what's going on around you,
 In order to judge where you must be, you must pay attention to the situation.  Where is the enemy?  Where are your comrades?  Where does terrain limit movement?  Is that other unit on our flank about to get crushed?  Which way are we moving now?  The best phrase to sum up this concept is the one used by military forces around the world; "Stay alert and stay alive".

Someone has to be in charge,
 "For God so loved the world that he did not send a committee."  It's an old joke, but true nonetheless.  Democracy is a wonderful system that works well in times of peace, but it's unsuited to warfare.  Time counts on the battlefield, so there's no time to reach a consensus.  Listen to the commander and follow orders.  If you don't like the commander, tough!  If you're going to be an individual and run off and do your own thing once the fighting starts, then you're going to get some of us killed.  Let me sum up with another quote, attributed to Benjamin Franklin after the signing of the Declaration of Independence:  "We must all hang together, or we will assuredly hang separately."

Stay mobile,
 Mobility is key to success on the battlefield.  It allows us to pick where we will fight, when we will fight, and under what conditions we will fight.  It can be used to string-out a tight unit or pack together a loose unit.  If we can't go through it we can go around it.  All other factors being equal, the unit with the most mobility will tend to win the fight.  Once we pin a unit, we can cut them to pieces at our leisure.  If a unit can't pin us down, they can't kill us.

Sometimes you have to leave your buddies behind,
 This is a touchy subject, but must be covered.  We are a unit.  If the unit wins, we all win, if an individual wins, the group can still lose.  Nobody likes to leave a friend behind (no one that I'd associate with), but sometimes it is necessary.  If that person has run off to fight on their own or lost their mobility due to a wound then they are on their own.  The unit must remain mobile, and cannot do this with a gimp.  Speaking for myself, I would be ashamed to have the unit lose because it was trying to protect me.  Better to lose one or two warriors than five or ten.
 This also applies to the enemy.  Leave the gimps.  A man on his knees can still fight and kill.  If we gimp five or six of the enemy then we can take them out of the equation simply by rotating our front to focus our attacks on our unwounded foes.  A smart foe won't let this happen, but most of them will.  Do the math:  Ten on ten.  We gimp three and rotate our front so that the gimps can't attack us.  Ten on seven.  Once the entire unit is dead or gimped we can leave all of them where they lay and move on to attack another unit.  Don't over focus and let a pocket of gimps cripple our force.  Leave them, destroy their buddies who can still walk around, and come back to them later when we can take our time and pick them apart with spears.

Take small bites and keep chewing,
 To defeat twenty warriors with ten, we kill two of them with four of ours.  Do it suddenly, violently, and above all, quickly.  This is known as concentrating our forces to achieve local numerical superiority.  The odds are now eighteen to ten.  We do it again, and again, and again.  We use our mobility, string them out and isolate individuals, gimp one and leave him.  Soon the odds will be eight to ten and we will be able to overwhelm them.  To do this we must apply all the aforementioned principles.  We must be smooth, practiced, aggressive, and fast.

Fight on the oblique,
 Because SCA combat is primarily oriented towards tournament style fighting in which two individuals (or two small groups) square off and slug it out, people in the SCA tend to carry this attitude into a melee.  When faced with an opposing force they seek to come face to face with an opponent and fight.  The SCA rules further encourage this by preventing attacks from the rear or a blind flank.  It is still possible to hit someone where they aren't looking (the best place to hit someone from).  We do this by attacking on the oblique.  Simply put, if you are part of a battleline facing an opposing battleline, then you should not attack the person directly in front of you.  Instead, fix the person in front of you, get them to focus on you, and then attack the opponent one or two down from you.  If you can't do that, then engage the opponent in front of you and get him to open up to an attack from another member of our group.
 On a larger scale this means not hitting a battleline head-on.  Hit them from an angle.  In this way all of our forces can engage a portion of their forces.  We gain local superiority in numbers, we dictate the terms of the engagement and force the enemy to adjust, and we keep one of our flanks open in case we need to maneuver.

Don't do stupid things,
 If you forget everything else, remember this.